[Bug #1049] Fix bug

Milestones don't have calendars and the calendar of the task was
always reattached.

FEA: ItEr74S04BugFixing

navalplanner-webapp/src/main/java/org/navalplanner/web/planner/order/EditTaskUtilities.java

@@ -83,6 +83,9 @@ public class EditTaskUtilities implements IEditTaskUtilities {
 
     private void reattachAndLoadCalendar(TaskElement taskElement) {
         BaseCalendar calendar = taskElement.getCalendar();
+        if (calendar == null) {
+            return;
+        }
         baseCalendarDAO.reattach(calendar);
         forceLoadCalendar(calendar);
         calendar.getCapacityOn(